( 1. 國防科技大學 航天與材料工程學院 新型陶瓷纖維及其復合材料國防科技重點實驗室，長沙 410073；
2. 西北工業(yè)大學 凝固技術國家重點實驗室， 西安 710072)
摘 要: 從非穩(wěn)態(tài)傳熱角度并按照柱坐標系中二維傳熱方式對Bridgman裝置中Al柱狀試樣近快速定向凝固過程進行了數(shù)值模擬，分析了試樣在近快速定向凝固過程中液固界面前沿的溫度梯度和生長速度隨試樣抽拉速度的變化規(guī)律。 計算結果表明： 在30～3000μm/s的抽拉速度范圍，隨著抽拉速度的提高， 液固界面前沿的溫度梯度在（145±10）K/cm范圍變化， 生長速度與抽拉速度的差別不超過5%。 研究結果為實驗研究近快速定向凝固組織形態(tài)轉變提供了可靠的控制參數(shù)依據。
關鍵字: 近快速定向凝固； Al柱試樣；數(shù)值模擬； 溫度梯度； 凝固速度
Al bar sample
（ 1. Key Laboratory of National Defense Technology for Advanced Ceramic Fibers and Composites,
College of Aerospace and Materials Engineering,
National University of Defense Technology,
Changsha 410073, China;
2. State Key Laboratory of Solidification Processing,
Northwestern Polytechnical University, Xi′an 710072, China）
Abstract: An universal method of numerical simulation on near-rapid directional solidification of Al round bar in a vertical Bridgman furnace was developed, in which the transient heat transfer equations were used and the longitudinal heat conduction is taken into account. The influence of pulling velocity on the temperature gradient and growth velocity of liquid-solid interface was analyzed. The results indicate that, in the pulling velocity range of 30～3000μm/s, the change of pulling velocity on the temperature gradient and growth velocity of liquid-solid interface is hardly obvious. With pulling velocity increasing, the temperature gradient is changed from 135 to 155K/cm, and the difference of growth velocity and pulling velocity is within the range of 5%. The numerical simulation of the near-rapid directional solidification of Al sample can provide an available tool for the investigation on the selection of microstructure of binary sing-phase Al-Zn alloy under near-rapid directional solidification condition.
Key words: near-rapid directional solidification; Al round bar sample; numerical simulation; temperature gradient; growth velocity
